Diets rich in fiber, plant protein, and unsaturated fat may beneficially modulate the gut microbiota involved in weight loss

In a recent review published in the Nutrients Journal, researchers reviewed existing data to evaluate the impact of macronutrients and diet patterns on the gut microbiome among overweight and obese individuals.

Study: Effects of Animal and Vegetable Proteins on Gut Microbiota in Subjects with Overweight or Obesity. Image Credit: AntoninaVlasova/Shutterstock.com

Background

Obesity, or adiposity, is an increasingly prevalent multifactorial condition that increases the risk of non-communicable-type diseases such as cardiovascular diseases, metabolic disorders, diabetes, and musculoskeletal disorders, degrading life quality and lowering overall survival.

The microbes in the gut, or intestinal microbiota, are critical to preserving health and preventing obesity, identifying which could aid in developing targeted weight loss strategies based on intestinal microbial modulation.

About the review

In the present review, researchers determined the association between dietary patterns, the gut microbiome, and obesity.

The PubMed database was searched for clinical trials, original research, meta-analyses, and reviews published in English up to February 2023 that assessed the influence of various macronutrients and diet patterns on the intestinal microbiome among overweight or obese individuals and mice.

In addition, the citations of the included records were searched manually to identify additional studies.

Studies with protein representing ≥ 20.0% of total daily energy or >1.30 grams per kg of body weight per day were included. The team excluded studies including normal-weight individuals, unpublished records, studies published in a non-English language, or records with unspecified protein intake.

Effects of carbohydrates, proteins, and fats on the gut microbiome

Consumption of carbohydrates such as whole grain or wheat bran can increase the abundance of Bifidobacteria and lactobacilli and increase gene richness, whereas the counts of Eubacterium rectale and the Firmicutes to Bacteroidetes ratio decrease.

Inuline-type fructans increase short-chain fatty acid (SCFA) levels and Bifidobacterium adolescentis abundance. Diets high in resistant starch (RS) and reduced carbohydrate weight loss (WL) diets increase Ruminococcus bromii and Oscillibacter counts and decrease Collinsella aerofaciens counts.

High-fat diets are associated with increased Alistipes and Bacteroides counts and lipopolysaccharide (LPS) levels and decreased Faecalibacterium counts and SCFA levels. Low-fat diets increase the fecal abundance of Bifidobacterium, and highly saturated-fat diets increase Faecalibacterium prausnitzii abundance.

Sardine-rich diets decrease the Firmicutes to Bacteroidetes ratio and increase the Bacteroides to Prevotella ratio. Omega-3 supplementation can elevate Coprococcus and Bacteroides species and reduce Collinsella species (related to fatty liver) counts.

Salmon and cod intake decrease Bacteroidetes abundance, whereas polyunsaturated fatty acid (PUFA) consumption can increase Lachnospiraceae and Bifidobacterium species abundance.

High-beef diets increase Bacteroides fragilis and vulgatus counts and decrease those of Bifidobacterium adolescentis.

Consuming concentrated whey from milk fermented with Bifidobacterium breve can lower Bacteroides fragilis and Clostridium perfringens counts. High-protein and low-carbohydrate diets can decrease Roseburia and Eubacterium rectale abundance and increase Akkermansia counts and gut microbial diversity.

Effects of different diets on the gut microbiome

Western diets, characterized by low fiber and high fat, meat, and animal food intake, increase the inflammatory bacteria profile, i.e., the abundance of Fusobacterium nucleatum, Alistipes, Bacteroides, Bilophila, Bifidobacterium, Peptococcus, and anaerobic Lactobacillus.

On the contrary, the levels of Firmicutes that metabolize plant polysaccharides (Ruminococcus bromii, Eubacterium rectale, and Roseburia) decrease.

Mediterranean diets (MED) are rich in plant-based foods and vegetables, with fish and poultry replacing lamb and beef intake, with limited red and processed meat intake, 40.0% of total calorie intake per day mainly from unsaturated fat, and daily protein and carbohydrate intakes of 123 grams and 80 grams, respectively.

Green-MED diets include daily intakes of green tea and the Mankai plant, rich in polyphenols. The diets increase butyrate-producing, beneficial, and anti-inflammatory bacterial counts, gene richness, and bacterial diversity in the gut.

MED diets increase Prevotella, Prevotellacea, Lachnoclostridium, Enterohabdus, and Bacteroidetes counts, elevate fecal propionate and butyrate levels, and enhance enzymatic degradation of branched-chain-type amino acids. On the contrary, Bifidobacterium, Lachnospiraceae, and Parabacteroides counts are lowered with the reduced enzymatic synthesis of branched-chain-type amino acids.

MED diets increase levels of the fiber-degrading Faecalibacterium prausnitzii and genes for microbial carbohydrate degradation associated with butyrate metabolism. Vegetarian diets are rich in vegetable protein, increasing Streptococcus and Anaerostipes counts while decreasing Clostridium and Odoribacter counts.

Low-fat vegan diets are associated with increased Bacteroidetes, Faecalibacterium prausnitzii, Prevotella, and decreased Bacteroides fragilis counts. Very low-calorie ketogenic diets
(VLCKD) are composed of about 26 grams daily carbohydrate intake, 40% of total daily energy from fats, and 90 grams daily proteins, about 1.20 to 1.40 grams/kg.

VLCKDs increase the abundance of Bacteroidetes, Ruminococcaceae, and Morigibacteriaceae and decrease that of Firmicutes, Proteobacteria, Enterobacteriaceae, Comamonadacea, and Sinobacteraceae.

Conclusion

Based on the findings, a higher intake of animal proteins and adherence to Western diets can decrease the abundance of beneficial bacteria and increase that of harmful bacteria in the gut, increasing obesity risks.

Contrastingly, increasing the intake of plant-based proteins and following Mediterranean diets increase the counts of butyrate-producing anti-inflammatory bacteria, lower those of pro-inflammatory bacteria, and increase bacterial diversity.

Increased intake of plant proteins, fiber, and adequate amounts of unsaturated fats may modulate the gut microbiome and aid weight loss.

Written by

Pooja Toshniwal Paharia

Dr. based clinical-radiological diagnosis and management of oral lesions and conditions and associated maxillofacial disorders.